OCC option symbol (OSI format)
The OCC option symbol is the standard 21-character identifier of a listed US option: the underlying root padded to six characters, the expiration date as YYMMDD, C or P for call or put, and the strike multiplied by 1,000 on eight digits. It replaced the older short codes in 2010 and is how data feeds and APIs name contracts.
Senzoukria · Glossary · Updated September 2026
At a glance
- Structure
- Root (6) + YYMMDD (6) + C/P (1) + strike × 1,000 (8)
- Length
- 21 characters in the padded form
- In effect since
- 12 February 2010 (Options Symbology Initiative)
The four parts
The Options Clearing Corporation's Options Symbology Initiative defined one symbol per contract that states everything needed to identify it. The root is the underlying's option symbol, padded with spaces to six characters. The expiration follows as year, month and day on six digits, then a single letter, C for a call or P for a put. The strike comes last, multiplied by 1,000 and zero-padded to eight digits, so five digits before the decimal point and three after.
| Symbol | Underlying | Expiration | Type | Strike |
|---|---|---|---|---|
| SPY260620C00500000 | SPY | 20 June 2026 | Call | 500.00 |
| QQQ260530P00499500 | QQQ | 30 May 2026 | Put | 499.50 |
| SPX 141122P01950000 | SPX | 22 November 2014 | Put | 1,950.00 |
Variants you will meet
- Many APIs drop the padding spaces and write the root directly followed by the date, as in SPY260620C00500000.
- Weekly and non-standard index series use their own root, for example SPXW for the PM-settled weekly S&P 500 options, which distinguishes them from the monthly SPX series of the same date.
- Adjusted contracts after corporate actions often receive a modified root, such as a digit appended, signalling a non-standard deliverable.
- Some platforms prefix the symbol with a character or use their own internal ids; convert before joining data sets.
Why the format matters for data work
Because the symbol is deterministic, it can be built from a chain's expiry, type and strike and used as a key to join trades, quotes, greeks and open interest from different sources. Errors usually come from the strike field, a strike of 499.5 must be written 00499500, and from roots: treating SPXW and SPX as the same underlying mixes two settlement methods.
In Senzoukria
Option Flow builds OCC symbols without padding, underlying plus YYMMDD plus C or P plus the strike times 1,000 on eight digits, for every contract in its window, uses them to request trades from the provider and to attach the latest chain's greeks and open interest to each print. The full symbol, together with the print's timestamp, price and size, forms the identity key of each print in the tape, which is how duplicate prints returned by successive polls are recognised.
Related
In the same section
- OFI
- Objective function
- OCO order
- NQ futures
- One-timeframing
- Notional value
- Open interest
- Non-professional status
Sources
- Wikipedia — Option symbol (OCC format) (2026-09-25)
This page in other languages
Frequently asked questions
- How do I read the strike in an OCC symbol?
- Take the last eight digits and divide by 1,000. 00500000 is 500.000, 00499500 is 499.500 and 01950000 is 1,950.000. The fixed width allows strikes up to 99,999.999.
- Why does SPXW have a different root from SPX?
- Because they are different option series on the same index, with different settlement: SPX monthly options are AM-settled on the special opening quotation, SPXW options PM-settled on the close. The root keeps them apart even when they expire on the same date.